I actually used 69 cast 340 exhaust manifolds, which by the way work pretty well, on a 340 with W-2 heads back 20 years ago. Worked just fine and the sound was awesome. I ground out the openings to fit the W-2 exhaust gasket. The guy that we sold it to said that there was virtually no difference between his Hooker headers and my worked over manifolds. Guess that Mopar engineers had some idea as to what works back in the late 60's.
